Nigel Slater: Perfect timing

Of all the pleasures that lie in wait for us in the kitchen, few can equal that of catching a fruit at its moment of perfect ripeness. Imagine a mango, its golden flesh so soft and full of juice it is almost too slippery to hold. Or a peach so perfect you must bite and suck at the same time to stop its rose-scented syrup running down your chin and arms.

Ripeness may, in the case of a pear, be quite fleeting. Others, tomatoes for instance, hold well for a few days, giving us time to hunt out a supply of decent basil and the best mozzarella di buffala to go with them. I must admit to being obsessed with the whole business; even more so now that the melon, mango and tomato season is upon us.

It is easy to miss the moment. For a few glorious weeks in May and June, it is the Alphonso mango season. There is no fruit in which ripeness - and our attention to its progress - is more important. I look forward to these fruits from Maharashtra in western India as much as I do the asparagus or wild salmon whose season they share. If you venture to Southall in Middlesex or wander along Drummond Street by London's Euston station any time in the next few weeks, you will find small boxes of dull, yellow-skinned fruits sporting sprigs of pink and purple tinsel - their season is truly something to celebrate.

I have a box of them in the kitchen right now. They have all ripened at once and we will pig out on them this weekend for breakfast, lunch and after the evening meal. Mango-watching is a favourite hobby of mine, checking out their progress every day, turning them so they ripen evenly. As they soften they become more fragrant, a sweet honeyed smell with the faintest hint of resin. When ready, they may show a bud of nectar at the stalk end, and will have fine wrinkles. If their skin has blotches of black and smells of paint stripper you have blown it.

Mangoes are an embarrassing fruit to tackle even among mates. Peel them instead and serve them with a small fork stuck in each end, then there might be takers. There is talk of untimely rains in India this year, which might explain the vast barrow of cut-price fruits I saw in Selfridges the other day, a member of staff tempting passers-by with a wedge of deep golden flesh on a cocktail stick. I went back three times.

Melons are less reliable. I had several last summer that never ripened at all. They were mostly Honeydews, the ones that look like a bright yellow rugby ball. The smaller, green-striped Charentais and the larger Ogen are easier to gauge. Ogen melons have juicy green flesh and a greeny-yellow skin that is covered with an intricate, rough webbing. This 'netting' can be used as a sign of ripeness. The more pronounced the netting the riper the fruit. But all this is rather academic. The soundest way to suss out your Charentais is with your nose. A ripe melon is a deeply fragrant melon. Its skin should give a little at the fruit's North and South Pole.

Colour and smell are little use when it comes to assessing the ripeness of an avocado. Again, there will be some dulling of the skin, but the real and only test is to use your hands. It makes me laugh when greengrocers refuse to let you pick out your own, and yet ask most of them to find you a ripe avocado and they will poke at them like they are trying to wake a sleeping teenager. What works for me is to hold the pear in my right hand and give it a slow, gentle squeeze using the whole hand. The thumb should barely come in to it. That is why I like the Hass variety. Clumsy customers can do it less harm than the thin-skinned green Fuerte.

I used to curse the shops for not selling fruits ripe and ready to eat. I know better now. You will get a mango, a pawpaw or an avocado home in better condition if it is underripe. It is then up to us to nurture it towards spot-on softness. A cool room will do. Fruits need to be kept apart, especially thin-skinned pawpaws which will turn to slush where they touch one another.

I still meet people who don't believe the paper-bag trick. Take a ripe fruit - a banana is the most efficient for this - and wrap it in a large brown paper bag along with the unripe fruit. Leave it for a day or two and by that time the unripe fruit should be well on its way. Better still, is to give your fruit time to mellow naturally, sniffing and fondling it as the days progress, each one bringing you a step closer to that brief moment of perfect, sublime ripeness.

Mango and cardamom lassi

As much as I have enjoyed the mango lassi I drink in India, I make it differently at home. I always include a touch of cardamom - no more than six or eight of the little black seeds you find inside the green shells - chucked into the blender with the other ingredients. It makes what can be a slightly bland drink instantly more interesting. The riper the mango, the more satisfying the drink.

Pour the yogurt into the jug of a blender with the milk or mineral water (water will make your drink more refreshing, milk more creamy). Peel the mango and slice off the flesh into the blender.

Crack open the cardamom pod and remove six or eight of the black seeds. Sprinkle them into the mango and yogurt, drop in the ice cubes and blend until completely smooth.

Taste it for sweetness. I don't add sugar to mine, but this is quite inauthentic - around Bombay they take a lot of sugar in their lassi. A couple of teaspoons for this quantity should be enough.

Mango sorbet and vanilla ice cream

Good though mango sorbet is, it gets even better when you serve it with a good vanilla ice cream. I am happy enough to buy the vanilla ice cream but prefer to make the mango sorbet myself. Believe me, the combination is joyous. Serves 4.

Put the sugar in a small stainless-steel pan, pour in 250ml of water and bring towards the boil. As soon as the sugar has dissolved, remove from the heat and leave to cool. Chill thoroughly.

Peel the mangoes, then slice the flesh over a bowl to prevent any of the juices escaping. Whiz the flesh and the lime juice to a smooth purée in a blender.

Mix the mango and chilled syrup together then pour into an ice-cream machine. Let the sorbet churn until it is starting to freeze, then whisk the egg white till thick and firm and fold into the churning sorbet. This will lighten the sorbet. Quickly remove from the machine and transfer into a freezer box. Freeze till firm. Alternatively, pour into a freezer box and freeze, removing every few hours to whisk the ice crystals forming around the edge into the middle. It will take a good 4 to 6 hours to make it this way.

Mango sorbet freezes quite hard. Give it 20 minutes plus in the fridge to soften. Serve one ball of mango sorbet and one of vanilla ice cream to each guest.